I'll try to have my bags checked through to final destination and we have Nexus, but it still sounds like 1.5-2 hours would be a safe bet.
Since you’ll have to wait for your bags and clear customs at ORD*, having them “checked through” doesn’t save much time. Yes, you can drop off your bag after customs without needing to stop by an agent, but that doesn’t save much time.
If it takes 45 minutes to get your bags, 1.5-2 hours is anything but a “safe bet”.
(* the only exception would be if you arrive at T5 from a pre-clearance airport like Dublin or Doha. But then you've already passed immigration as well, so Nexus wouldn't matter.)